Patient ambulation motion detector

ABSTRACT

A patient ambulation motion detector is intended for attachment to a lateral generally vertical surface of a patient&#39;body. The detector includes a motion sensor switch and a detachment detector switch which are mounted on a circuit board, the circuit board being in turn enclosed within an attachment casing which is attachable to a lateral surface of the patient&#39;s body. The motion sensor switch is a mercury switch mounted to the circuit board and having the axis of movement of the mercury contained therein oriented generally parallel to the circuit board so as to be responsive to declination of that portion of the patient&#39;s body to which the detector is attached and which declination is indicative of impending ambulation. The detachment detector switch is a spring contact switch which is openable and closable by a plunger acting thereon and sensitive to detachment of the detector from the patient&#39;s body. The detector may be wired to a conventional switched nurse call system.

BACKGROUND AND SUMMARY OF THE INVENTION

The present invention relates generally to devices and methods formonitoring patient activity, and particularly to means for detecting themovement of a patient in a bed from a horizontal, i.e. prone or supineposition to an erect or semi-erect position, as in an attempt by thepatient to get out of bed preparatory to ambulation.

It is often desirable to ensure that hospital patients remain supine orkeep to their beds, especially after and while recovering from surgery,and when bed rest is absolutely required. It is also often desirable forhospital personnel to directly monitor the physical activity of apatient without actually being in attendance at the patient's bedside,so as to be aware of any activity which may be deleterious to thepatient's condition. Thus, it is often desirable to monitor a patient inorder to detect, and therefore be able to avoid, the anesthetizedpatient, as upon partially regaining consciousness after coming out ofsurgery, getting out of bed (or making an attempt to do so) when suchactivity may place the patient, who may not be aware of his/her owncondition, at risk. At the same time, the use of restraints isundesirable, for obvious reasons, making it necessary for attendingpersonnel to personally monitor the patient's activity level in order toassure the patient does not make or undertake any movement which mightjeopardize the patient's condition. Typically, it might be desired toguard against the patient getting out of bed, however such might not bedetected by hospital personnel until the patient has actually done so.Thus it is desirable for hospital personnel to be able to detect whenthe patient is attempting to, or in the process of alighting the bedpreparatory to patient ambulation, and to alert the hospital personnelof this impending activity, so as to permit the hospital personnel toattend the patient before alighting and ambulation actually proceed. Thepresent invention is directed to a means for making possible such earlydetection of patient movement indicative of impending patientambulation.

More particularly, the present invention is directed to a device whichattaches easily and unobtrusively to a lateral surface of the thigh orother portion of the body of a patient and which is sensitive toattitudinal changes in the orientation of the patient's thigh or body sothat an alarm signal is produced thereby when the patient attempts tostep out of bed preparatory to ambulation, this alarm signal preferablybeing transmitted over the "nurse's call" system for alerting attendinghealthcare personnel of the patient's activity. Additionally, the deviceprovides an alarm signal if it is removed or becomes dislodged from thepatient. Advantageously, the alarm signal remains on until reset at thedevice, in distinction to a normal nurse call signal which may becancelled at the nurse's station console, thus indicating to attendingpersonnel that the alert signal is from the patient ambulation motiondetector device and not simply a nurse call signal.

The patient ambulation detector device of the present invention isself-attaching and is adapted for attachment to either the right or leftthigh of the patient. The device is compact, simple in construction andrelatively inexpensive to manufacture. Further, the device can be easilyconnected to existing nurse call systems, typically without any systemmodification being required.

A number of devices for monitoring bed-patient movement have beenpreviously proposed. One such device is disclosed in U.S. Pat. No.4,536,755 of Holzgang et al., and includes a mercury switch mounted on acircuit board and constituting an angle inclination sensing means forsensing angular displacement of a patient's upper leg relative to areference datum plane. In this prior device, the circuit board with themercury switch mounted thereon is housed in an enclosing carrier modulewhich is strapped to the patient's thigh by means of an elastic band soas to be positioned on the anterior, i.e. upper surface of the patient'sthigh, i.e. femur. An adhesive-backed foam pad is attached to the rearwall of the carrier module to serve as an interface between thepatient's thigh and the module, to secure the device in place and toenhance patient comfort. In order to detect the unauthorized removal ofthe device from the patient's thigh, the device also includes a pressureswitch having contacts which project from the lower surface of thecircuit board and extend through an aperture in the carrier module rearwall to engage the anterior surface of the patient's thigh. Sensing ofthe downwardly directed angular inclination of the distal end of thepatient's femur is accomplished by orienting the mercury switch on thecircuit board so that, when the device is secured to the patient'sthigh, an upwardly or downwardly directed angular inclination of thefemur portion of the patient's leg proximal the knee has the effect ofadjusting the position of the mercury contained in the switch. In thisway, a downwardly directed inclination of the patient's leg whichexceeds a preselected inclination threshold angle will bring the mercurywithin the switch casing into contact with a pair of respectiveelectrodes to form a closed conduction path therebetween, effectingclosure of the switch and applying battery voltage to a time delaycircuit and thence to the gate electrode of an SCR, thereby switchingthe SCR on. When switched on, the SCR supplies current to an alarmcircuit oscillator stage which generates audio frequency tone burstswhich are applied to an audio transducer for producing an audible signalto indicate to attending personnel that the patient is in an "ambulatoryenabling" position. Unauthorized removal or dislodgement of the devicefrom the patient's thigh causes the pressure switch to close, which inturn causes immediate sounding of the audible alarm signal.

This prior device has only limited usefulness, for several reasons.Being battery powered, it is susceptible to becoming inoperative due tothe battery running out. Additionally, the device only produces an audioalarm signal from the self-contained audio transducer, which alarmsignal may not be audible to hospital personnel located, for example, ata nurse's station some distance from the patient's room, especially ifthe door to the patient's room is closed. Further, the audio alarm maynot be audible above or distinguishable from background and other noise,such as paging messages, in the hospital ward. It is suggested that aradio transmitter might be substituted for the audio transducer toproduce an inaudible warning signal for reception at a remote location.However such a system is still susceptible to inoperability due to adead or low battery, and requires the additional expense of installingreception means at each necessary location for alerting the responsibleattending personnel.

Another prior device of this type which utilizes a specially configuredmercury switch position sensor is disclosed in U.S. Pat. No. 4,348,562to Florin. This disclosed device is described to provide an alarm systemwhich is capable of being integrated with existing hospital call systemsso as activate a patient's call light and/or buzzer, thereby notifyingthe nurse of the exact location of the patient at risk. Such integrationwith existing call systems would be advantageous also in that noadditional power supply would be required.

This prior device monitors changes in position from the horizontal ofthe anterior surface of a patient's chest or thigh towards a morevertical orientation which may signify impending injury due to a fall orrising of the patient. The device uses a particularly configured specialmercury switch casing designed with a large head chamber, in which amercury ball normally resides, connected via an axial throat passage toa smaller foot chamber wherein are provided spaced-apart electrodes.Basically, the head chamber and its transition region with theconnecting throat passage are so configured as to prevent the mercurypassing into the throat passage until the angle of inclination of theanterior body surface of the patient to which the device is attachedexceeds 70° from the horizontal, while the foot chamber is made deep, sothat once the mercury has moved down into the foot chamber and switchclosure has thereby been effected the mercury is prevented from flowingback out of the foot chamber into the throat passage and opening theswitch until the switch assembly is inverted to a 90° head-down positionfor thus resetting the device.

This described prior device is fashioned by forming the chambers andconnecting passage in a plastic block into which are led connectingwires the ends of which are bared and particularly disposed in the footchamber for providing the switch contacts, with closure lids beingfastened atop and below the block. A removable adhesive is applied tothe bottom surface of this assembly in order to prepare it forapplication to an anterior horizontal surface of the patient.

However, this prior device also has limited usefulness, due in part tothe cost and complexity of fabricating the specially configured chambersand connecting passage. Also, both this prior device of Florin and thepreviously noted prior Holzgang et al. device are both required to bepositioned on an anterior surface of the patient's body for obtainingtherefrom a horizontal plane datum, and are consequently obtrusive.Further, in practice the disposition of the anterior surfaces of apatient's body may not in fact lie on the horizontal but rather may tendto be more or less inclined when the patient is lying in bed, and willnaturally tend to move inclinedly along with normal body movements asduring breathing. Also, it may be the case that portions of thepatient's body, and hence its anterior surfaces, are intended to beinclined or reclined for various reasons such as to promote drainage,assist respiration or maintain traction or flexure, in which case amonitoring device which necessarily requires attaching at an anteriorhorizontal body surface may not be at all suitable.

The sensing of the patient's physical position and movement with anordinary gravity mercury switch used as a motion detector isadvantageously convenient, as ordinary mercury switches are small,sensitive and widely available at reasonable cost. However, when amercury switch type device is designed to be attached or positioned onan anterior, i.e. horizontal portion of the supine patient's body, itbecome necessary to orient the ordinary mercury switch itself generallyvertically inclined or upright in order to be sensitive to verticalinclination movement relative the horizontal datum plane, and thus thedevice enclosure must be made sufficiently large to accommodate theheight of the generally vertically oriented mercury switch bulb, makingthe device bulky and obtrusive, or a specially configured custom mercuryswitch must be utilized as in the noted Florin device having the mercuryswitch in a generally horizontal disposition, in order to obtain a lowerheight aspect while remaining insensitive to normal slight motion aboutthe horizontal datum.

Other prior devices for monitoring patient movement or for providing analarm upon impending vacating of the bed by the patient are known fromU.S. Pat. No. 4,179,692 to Vance; U.S. Pat. No. 4,583,084 to Hendersonet al.; and U.S. Pat. No. 4,633,237 to Tucknott et al.

The present invention provides a patient ambulation motion detectordevice of the mercury switch type which overcomes the limitations of theconventional devices, and which is unobtrusively positionable on alateral surface of the patient's body, whereby it is made possible toutilize a generally vertically inclined ordinary mercury switch in sucha device for reliable detection of patient body motion relative thehorizontal datum plane. The present invention also provides a patientambulation motion detector of the mercury switch type which is of simpledesign, having only three electrical components, one for sensing patientmotion, one for detecting detachment of the device and one serving formounting and interconnecting the other two, and which is connectable toconventional hospital nurse call systems.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other characteristics, features and advantages of the presentinvention will become more apparent from the following detaileddescription taken with reference to the accompanying drawings, in whichlike elements among the various figures are designated with likereference numerals, and in which

FIG. 1 is a pictorial representation showing a device in accordance withthe present invention in use;

FIG. 2 is a schematic circuit diagram of a device in accordance with thepresent invention;

FIG. 3 is a side view of a device embodied in accordance with thepresent invention;

FIG. 4 is a top view of the device embodied in accordance with thepresent invention;

FIG. 5 is a bottom view of the device embodied in accordance with thepresent invention;

FIG. 6 is an exploded view of the device embodied in accordance with thepresent invention; and

FIG. 7 is a plan view showing the electrical component arrangement ofthe device embodied in accordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to FIG. 1, there is shown by the solid line and viewedfrom the right side, the outline of a person such as a hospital patientdesignated generally at P laying down in a supine generally horizontalposition. The position of the patient P, having assumed a generallyupright position with the upper torso raised to a generally verticalorientation and with the right leg inclined generally downwardly as instepping from a bed prior to ambulation, is depicted generally by thedashed or broken line outline at P'.

Shown positioned on the outer lateral surface of the right thigh of thepatient P, P' is a patient ambulation motion detector device accordingto the invention, designated generally at 10.

Referring now to FIG. 2, there is shown in partial schematic and partialpictorial form an electric circuit of the device 10 embodying theinvention. Within the circular dashed outline (representing a printedcircuit board and enclosure as detailed below) there is shown a parallelcircuit of an SPST glass bulb/tube type mercury switch 12, which servesas the motion detector means of the device, and another SPST switch 14,which serves as the detachment detector means of the device, connectedacross a pair of respective signal/supply lines 16 and 18 which lines16, 18 may, for example, be brought out to the tip and ring terminals ofa phone-type plug 20. As shown, either the SPST mercury switch 12 or theother SPST switch 14 will, when made closed, connect the lines 16 and 18with one another into a current or voltage loop, and effectivelyconnecting the tip and ring of plug 20.

It should be noted that in FIG. 2 the mercury switch 12 is depicted withthe axis of the tube 22 thereof oriented in a substantially verticalposition, that is, inclined with respect to the horizontal bottom edgeof the page, such that the electrodes 16a, 18a (connected to lines 16and 18, respectively) are located at the higher, i.e. upper end of thetube 22 of the mercury switch 12 while the mercury Hg resides under theinfluence of gravity in the lower, i.e. bottom end of tube 22 away fromelectrodes 16a, 18a.

Now considering the circular dashed outline in FIG. 2 as representing aprinted circuit (i.e. PC) board 30 on which the lines 16, 18 and theswitches 12, 14 are provided, it will be understood that this circuitboard 30 lies on the vertical plane, i.e. parallel to the vertical planeof the page, and that the mercury switch 12 is depicted with the axis ofthe tube 22 also lying on the vertical plane parallel with the circuitboard 30. In practice, it may be desirable to mount mercury switch 12 tocircuit board such that the upper electrode end of the tube 22 is raisedor spaced away slightly from the circuit board with the lowermercury-residing end of tube 22 close to or contacting the circuitboard, thus inclining the upper electrode end of tube 22 upwardly withrespect to the lower mercury-residing end relative the circuit board 30,for reasons which will be made apparent below.

It may further be considered that the lines 16 and 18 depicted in FIG. 2may be formed as conductor traces provided on circuit board 30, and animplementation of the circuit of FIG. 2 embodied on a circular circuitboard 300 in accordance with the invention is shown in FIG. 7. Oncircuit board 300 there are provided conductor traces or lands 160, 180corresponding to lines 16, 18 and connected to respective conductors ofline cord 200. An SPST mercury switch 120 is mounted on circuit board300 and has its upper end electrodes 160a, 180a connected to theconductor traces 160, 180 so that a connection between conductors 160and 180 may be made by mercury Hg bridging the electrodes 160a, 180a ofswitch 120 when the circuit board 300 is rotated a sufficient number ofdegrees in the plane parallel to the page to cause the "ball" of mercuryHg to flow by gravity to the electrode end of the switch 120, i.e. whenthe electrode end of switch 120 is displaced so as to be in a lowerposition than the opposite mercury-residing end.

It will be recognized also that the mercury switch will be made closedwhenever the circuit board is sufficiently displaced about thehorizontal axis, i.e. made substantially perpendicular relative theplane of the page along a horizontal axis so as to bring the electrodeend lower than the other end of the mercury switch, in which case theball of mercury Hg will also be caused to flow to the electrode end andto bridge the electrodes 160a, 180a.

It will be appreciated therefore that if the device 10 incorporating thecircuit board 30 (300) having the mercury switch 12 (120) mountedthereon is in turn positioned for example with the circuit boardoriented flat upon, i.e. parallel with the side or lateral portion of apatient's thigh, i.e. on a substantially vertical surface of thepatient's thigh as depicted in FIG. 1, then declination of the patient'sthigh relative the horizontal, as upon the patient extending the thightoward the floor in stepping from a bed preparatory to ambulation, willbring the electrode end of the mercury switch 12 (120) increasinglylower relative the mercury-residing end until, due to increasingdeclination of the patient's thigh and the device 10 therewith, themercury Hg is caused by gravity to flow to the electrode end of theswitch tube and to bridge the electrodes 16a, 18a (160a, 180a), makingthe mercury switch closed and connecting the lines 16 and 18 (160, 180).

It will also be appreciated that the device 10 positioned thusly on thelateral surface of the patient's thigh will also be responsive to thepatient rolling over onto his/her side, because such motion will tend tobring the ends of the mercury switch tube more or less level with oneanother, which may cause the mercury to spread out along the lowermargins of the tube 22 (220) and which might allow the mercury Hg tocontact the electrodes 16a, 18a (160a, 180a). In this case, it may beadvisable to mount the mercury switch to the circuit board with theelectrode end of the mercury switch tube 22 (220) raised slightly fromthe circuit board with respect to the mercury-residing end of the switchtube in order to prevent the mercury reaching the electrodes when thepatient is laying on his/her side. On the other hand, it may be desiredto detect when the patient is on his/her side, in which case themounting of the mercury switch such that the electrodes 16a, 18a (160a,180a) are oriented substantially on the same plane and parallel with thecircuit board 30 (300) (and thus parallel with the patient's side) willpermit the mercury to flow along the bottom of the switch tube 22 (220)and to contact and conductively bridge the electrodes for making theswitch closed whenever the patient rolls onto his/her side such as tobring the axis of the tube 22 (220) parallel to the horizontal thusenabling sensing of such patient position.

There is also provided on the circuit board a second SPST switchdesignated generally at 140 which may advantageously take the form of apressure or plunger switch by means of which the switch 140 may serve tosense detachment of the device 10 from the patient. Switch 140 includesa conductive spring contact member 142 (corresponding to the movableswitch contact 16b in FIG. 2) which may for example be ofberyllium-copper and is mounted at a base end 142a thereof to thecircuit board 300. The base end 142a is electrically connected toconductor land 160. Spring contact member 142 also includes a medialbridge portion 142b which is at a higher level relative the circuitboard 300 than is the base end 142a, being for example formed byimparting an S-bend in the member 142 between the base end portion 142aand medial bridge portion 142b, which form also imparts a spring actionto the medial bridge portion 142b allowing it to bend relative thecircuit board 300.

The other, free contact end 142c of conductive spring member 142 is bentdownwardly towards the circuit board 300 so as to normally be urged, dueto the aforementioned spring action of the medial portion 142b, intocontact with an underlying portion of conductor land 180b (correspondingto the stationary switch contact 18b in FIG. 2). Thus, switch 140 isspring biased to a "normally closed" (NC) condition, whereas mercuryswitch 120 may be considered to function as a "normally open" (NO) typeswitch.

As shown in FIG. 6, a central hole is formed through circuit board 300,in a location underlying the medial bridge portion 142b of conductivespring member 142, in order to accommodate the passage therethrough ofthe shaft end 410 of a plunger member 400. Shaft end 410 abuts theunderside of the bridge portion 142b as shown in dashed outline in FIG.7. At its other end, plunger member 400 is provided with a pressureplate or flange 420, whereby force may be imparted to the plunger member400 for pressing the shaft end against the bridge portion 142b of member142 so as to lift the medial bridge portion 142b, and the free contactend portion 142c therewith, relative the circuit board 300, against thespring force of the member 142. In this way, pressure force on thepressure plate end 420 of plunger 400 exceeding the spring force ofmember 142 will cause the free contact end 142c of member 142 to belifted out of contact with conductor land 180b for thereby breaking oropening the electrical connection between lines 160 and 180.

In practice, with the device 10 attached or held fast to the patient P,the plunger 400 will normally be pressed inwardly by the contact betweenthe patient's body and the pressure plate end 420, and the spring forceof member 142 in combination with the surface area of pressure plate end420 are so selected as to enable such pressure force on the plunger 400to easily lift the free contact end 142c of member 142 out of electricalconnection with conductor land 180b, whereby the switch 140 is made openso long as the device 10 remains firmly attached or held fast to thepatient's body. It will thus be appreciated that the switch 140 servesto sense detachment or removal of the device 10 from the patient byconnecting the line 160 with line 180 for closing the circuit, whilemaintaining the circuit open so long as the device 10 remains in placeon the patient.

The circuit board 300 may conveniently be accommodated within a housingor enclosure formed of an upper casing 50 and a lower casing 60 as shownin FIG. 6, by means of which attachment of the device 10 to the patientP may be facilitated. Conveniently, the casing may be of molded plasticconstruction, and should in any case be of electrically insulativematerial.

Referring now also to FIGS. 3 through 5, the upper casing 50 includes ashallow dome or inverted bowl-shaped central portion 52 from a lowermargin of which extends radially outwardly a lip portion 54. The centralportion 52 is sized adequately to accommodate the circuit board withinits open interior, and thus may be quite shallow in depth from its lowermargin to a flattened apex portion 52a since, in distinction to theaforementioned prior device of U.S. Pat. No. 4,536,755, the mercuryswitch in the present invention does not need to be inclined verticallyfrom the circuit board and therefore presents only a minimal heightaspect to be enclosed.

The open lower margin of central portion 52 is closed by the lowercasing 60, the circuit board 300 being mounted fast therebetween. Thismay be accomplished by providing recesses 310 in the outer edge ofcircuit board 300 in register with threaded bosses 56 formed on theinner surface of central portion 52 of upper casing 50 and holes 62formed through lower casing 60, whereby the upper casing 50 and lowercasing 60 with the circuit board 300 therebetween may be fastenedtogether with screws 64 inserted through the holes 62 and recesses 310and engaging the bosses 56. As may be seen from FIG. 3, the lower casing60 is flush with the lip portion 54 of the upper casing 50. Also, thelower casing 60 is provided centrally therethrough with a hole inregister with the central hole in circuit board 300, for accommodatingpassage therethrough of the shaft portion 410 of plunger 400, while theunderside of lower casing 60 serves as a rear abutment stop of thepressure plate 420 for limiting the inward movement of plunger 400. Theplunger 400 may be retained in the lower casing 60 by, for example, aretaining clip inserted in a groove of the plunger shaft (not shown)between the lower casing 60 and circuit board 300 in order to preventthe spring force of member 142 from forcing the plunger 400 out too far.

The lip portion 54 of upper casing may be provided with a groove foraccommodating passage of the line cord 200. Lip portion 54 is preferablymade progressively thinner, i.e. tapered from its inner edge to itsouter peripheral edge as to be flexible so as to conform at itsperipheral portion with the curvature of the thigh lateral surface, andto this end lip portion 54 may include upper and lower arcuate cuts 54bformed therein proximate the lower margin of central portion 52 tofacilitate flexing and curving of the lip portion 54 around the lateralthigh surface of the patient.

The flat top 52a of the upper casing 50 may be provided with indicia 53thereon, for example an arrow or other marking pointing "up" to guidethe proper placement of the device 10 on the lateral surface of thethigh with proper orientation of the mercury switch motion sensing meansfor responding to patient motion indicating impending ambulation. Inthis regard, it will of course be understood that "up" in this sensemeans that orientation of the device when attached to a lateral surfaceof the patient's thigh (or other body portion) which accordingly orientsthe mercury switch in an open state with the patient supine as describedabove, but which orients the mercury switch in a closed state when thepatient's thigh is extended downwardly and inclined from the horizontal(or the patient's upper torso is raised up) as when stepping from a bedpreparatory to ambulation.

For attaching the device 10 firmly to the patient's body, a thin flatflexible annular or ring-shaped attachment member 55 such as of foam orfilm sheet and having adhesive on a bottom side thereof is placed overthe upper surface of lip portion 54 of upper casing 50 so as to beadhered thereto, and has an outer margin 55a which extends radiallyoutwardly of the lip portion 54 as shown in FIG. 5, whereby thisadhesive-coated bottom surface of outer margin 55a is substantiallyflush with the undersides of lip portion 54 and lower casing 60.

Attachment member 55 is open at its center to allow the central portion52 of upper casing 50 to project therethrough, and serves by theadherent fixation of its adhesive lower surface to the upper surface oflip portion 54 and radial extension outwardly thereof for adherentlyattaching the lip portion 54 and thus the device 10 proper flush to thesurface of the patient's body with a degree of fixation between thedevice 10 and the patient's body sufficient for forcing the plungerinwardly against the spring force of member 142 to open the switch 140.

Thus, it is only necessary to "stick" the device firmly against thepatient's body so as to adhere the exposed peripheral margin of theadhesive underside of attachment member 55 to the patient's body, inorder to obtain a large circular contact area therebetween over whichcontact area a substantial yet unobtrusive adhesion force is obtainedfor firmly, closely and adherently attaching the device to the patient.

The line cord 200 carrying lines 160 and 180 from circuit board 300 mayconveniently be passed through a groove 54a of lip portion 54 andthrough a strain relief 57 in central portion 52 of upper casing 50, tobe connected in known manner to a conventional nurse call connector (notshown) at the patient's bedside, for example by means of the phone plug20 which will be plugged into a corresponding phone jack of a nurse callcircuit. Line connectors 210, 212 may be provided in line cord 200 inknown manner for permitting disconnection of device 10 from the plugportion of line cord 200.

When connected to a conventional switched nurse call system as arecommonly installed in hospitals, the device will draw necessary powerfrom the nurse call system circuitry at the patient's bedside.

In operation, making or closing of the mercury switch motion sensorcircuit (120, 160, 180) of device 10 upon sensing of patient bodymovement preparatory to ambulation, and/or closure of the plunger switchdetachment sensor circuit (140, 160, 180) will switch the nurse call on,and because the nurse call circuit will not be resettable to off in anordinary manner at the nurse's station, the persistence of the on state,which will last until the patient once again resumes or is placed in asupine posture or until the device is reattached, will indicate to thenurse that the patient is in the process of getting out of bedpreparatory to ambulation (or, optionally that the patient has rolledonto his/her side), and/or that the device has been removed or becomedetached from the patient.

The device of the present invention may conveniently be provided inversions for attachment to either the left or right lateral surface ofthe patient's body as may be necessary or dictated by the proximity andlocation of the nurse call circuit connection, simply by utilizingsymmetrical "left" and "right" conductor layouts for circuit board 300,the other components being identical among the left and right sideversions since the versions need differ only with respect to thesymmetrical orientations of the mercury switches.

It will be readily appreciated that the above-described patientambulation motion detector device according to the present invention isamendable to various modifications within the scope of the invention.For example, the mercury switch might be configured with an arcuate orcurved rather than a straight bulb or tube, to provide differentresponse characteristics to motion about the horizontal datum.Accordingly, the scope of the present invention is intended to belimited only by the appended claims.

What is claimed:
 1. A patient's ambulation motion detectorcomprising:motion sensor means for sensing movement of a patient's bodyfrom a supine posture to a posture indicative of impending ambulationand for providing an electrical signal in accordance with said sensedmovement; attachment means for attaching the motion sensor means to alateral and substantially vertical surface of a supine patient's body;and detachment sensor means for sensing detachment of the detector fromthe patient's body and for providing an electrical signal in accordancewith said sensed detachment; wherein the detachment sensor meanscomprises: a planar circuit board provided with respective first andsecond conductor lands thereon and having an aperture provided centrallytherethrough; a conductive spring contact member having a base endconductively mounted to said first conductor land on said circuit board,a medial bridge portion extending from the base end and spaced above andat a higher level relative the circuit board than the base end, and afree contact end opposite the base end and overlying said secondconductor land on said circuit board and being elastically urged intoconductive contact therewith; and a plunger having a shaft portionpassing through the aperture in the circuit board, one end of said shaftportion abutting an underside of the medial bridge portion of theconductive spring contact member, said plunger being movable againstsaid conductive spring member for urging the free contact end of saidconductive spring contact member out of electrical contact with saidsecond conductor land on said circuit board.
 2. The patient ambulationmotion detector according to claim 1, wherein the motion sensor meanscomprises:a planar circuit board provided with respective first andsecond conductors; and a mercury switch mounted to the planar circuitboard and connected in parallel across said first and second conductors,the mercury switch having at one end thereof first and second electrodesconnected respectively to the first and second conductors, the mercuryswitch also having a longitudinal axis along which a mercury conductoris movable by gravity for conductively bridging said first and secondelectrodes and which axis is oriented substantially parallel with theplane of said circuit board.
 3. A patient ambulation motion detector,comprising:motion sensor means for sensing movement of a patient's bodyfrom a supine posture to a posture indicative of impending ambulationand for providing an electrical signal in accordance with said sensedmovement; and attachment means for attaching the motion sensor means toa lateral and substantially vertical surface of a supine patient's body;wherein the attachment means comprises; a circular upper casing memberhaving a shallow dome-like bowl-shaped downwardly opening centralportion from a lower margin of which central portion extends radiallyoutwardly a lip portion; a flat circular plate-like lower casing memberclosing the lower margin of the upper casing member and flush therewithand with said lip portion thereof; means for joining the upper and lowercasing members, said upper and lower casing members when joinedenclosing therebetween the motion sensor means; and a flat annularattachment member having a circular open center portion fitting aroundthe central portion of the upper casing, and having an annulus overlyingand extending radially outwardly of the lip portion of the upper casingmember, a bottom surface of at least that portion of said annulusextending radially outwardly of said lip portion being adhesivelycoated; wherein the lower casing member is provided with a centralopening therethrough for accepting a plunger.
 4. The patient ambulationmotion detector according to claim 3, wherein the central dome-likeportion of the upper casing member has a flattened top apex of which areprovided indicia for indicating proper orientation of said attachmentmeans on a lateral surface of a supine patient's body.